1. Field of the Invention
The invention relates to liquid two-component coating compositions based on amino-reactive resins, polyamine curing agents and aminourethanes. The coating compositions are useful in the coating of a wide variety of articles, especially in industrial coatings, automotive finishing and the coating of automotive components.
2. Description of Related Art
Because of environmental regulations, which are becoming more and more stringent, aqueous systems are gaining increasing importance for use in coating articles. In terms of their properties, they must be measured against conventional, i.e. solvent-containing systems. In this context, water-dilutable epoxy resin systems have gained importance among cold-curing water-based coating systems. These two-component systems have outstanding properties. The following positive properties are to be emphasized: little or no solvent content, not a fire hazard, little or no odor, ease of processing, low degree of sensitivity toward moist substrates, good drying and rapid through-hardening, excellent adhesion to most substrates, very good intercoat adhesion, good protection of metals against corrosion, and easy cleaning of equipment directly after use.
Nonionically dispersed epoxy resin systems, as described in DE-A 3 643 751, together with aqueous amine-based curing agents specified in EP-A 0 000 605, exhibit these outstanding properties and can therefore be used in a versatile manner as coating compositions. The disclosure of these documents and all other documents mentioned herein are incorporated herein by reference in their entirety. A disadvantage of these systems, however, is that they do not produce defect-free surfaces in certain applications.
EP-A 0 523 610 describes aqueous two-component systems based on epoxy/amines, which overcome the above-mentioned disadvantage by the addition of water-soluble or water-dilutable polyurethane resins. The system described in this document also brings about a high surface quality. These systems are intended to be used primarily in automotive refinishing. The disadvantage of these coatings, which are in particular fillers and primers, however, is that they have an inadequate sandability after a short drying time. Such systems are in general much too soft and, because of the pronounced thermoplasticity, after a short time the sand paper exerts a severe effect and the surface is damaged.
EP-A 0 234 395 describes aminourethane resins which are obtained by reacting carbonates with compounds having primary amino groups and further basic groups. Because of the incorporation of, for example, partially blocked polyisocyanates, these resins may be self-curing. However, it also is possible to add to the aminourethanes a curing agent which is conventional for coating systems which crosslink by means of external agents, for example, blocked polyisocyanates, .beta.-hydroxy esters of at least difunctional polycarboxylic acids, transesterification curing agents or Michael addition products. The aminourethanes are preferably employed, after at least partial neutralization, as resins for electrodeposition coating. There is only a very general indication that the aminourethane resins can also be employed in, preferably nonaqueous, coating systems containing epoxy resin. More precise details of the composition, use and properties of these coating systems are not given.